1. Field of the Invention
The present invention pertains to a tension regulator for elastic tape and the like, particularly in sewing machines adapted to attach tape to a workpiece.
2. Prior Art
When garment workpieces such as bathing costumes, underclothes and the like have to be made, it is rather usual that the finished workpiece needs to be pleated at different points; these pleats are generally obtained by stitching the material forming the garment workpiece on an elastic pre-tensioned tape or the like. In this manner, once the tape has taken its natural position again, the material stitched on said tensioned tape appears pleated proportionately to the tensioning of the tape during the stitching operation.
Normally the pre-tensioning of the tape is directly carried out by the operator acting manually on the tape; however this procedure depends greatly upon the dexterity of the operator and in any way it often gives rise to different results in different workpieces.
A device is also known for adjusting the tensioning of these tapes, substantially comprising a pair of knurled rollers between which the tape is caused to pass; these knurled rollers are moved by means of a free wheel device operated by a connecting rod, so as to adjust the feeding of tape to the pressing foot of the machine.
However this device can only effect activation in order to reduce the tensioning of the tape (in fact it is not in a position to take up tape, should the tensioning of the latter become slacker) and it also has further drawbacks. it is not responsive to variations in tape elasticity, so that, if the tape--due to defects in manufacture or the like--exhibits portions of greater or lesser elasticity than usually, it cannot adjust the tensioning of the tape based on a predetermined it, value. it also gives rise to difficulties when the predetermined tape-tensioning value has to be adjusted or when some values must be repeated owing to the fact that said adjustment is obtained by regulating the length of the connecting rod actuating the knurled rollers, a long and arduous operation. It also varies according to the type of tape used; and each time the sewing machine stops, the length of tape situated between the knurled roller and the presser foot of the sewing machine becomes unusable as it is no more possible to adjust the tensioning thereof.
Furthermore said device is rather bulky and is usually located close to the sewing machine's presser foot so that it interferes with the operator's work and reduces his visibility.